Disk-based storage devices such as hard disk drives (HDDs) are used to provide non-volatile data storage in a wide variety of different types of data processing systems. A typical HDD comprises a spindle which holds one or more flat circular storage disks, also referred to as platters. Each storage disk comprises a substrate made from a non-magnetic material, such as aluminum or glass, which is coated with one or more thin layers of magnetic material. In operation, data is read from and written to tracks of the storage disk via a read/write head that is moved precisely across the disk surface by a positioning arm as the disk spins at high speed.
The storage capacity of HDDs continues to increase, and HDDs that can store multiple terabytes (TB) of data are currently available. However, increasing the storage capacity often involves shrinking track dimensions in order to fit more tracks onto each storage disk, such that inter-track interference (ITI) becomes an important performance issue. Also, read/write head scaling is limited, so eventually the magnetic field used to write one track will impact adjacent tracks and thereby limit track density.
A number of additional techniques have been developed in an attempt to further increase storage capacity. For example, a technique known as shingled magnetic recording (SMR) attempts to increase storage capacity of an HDD by “shingling” a given track over a previously written adjacent track on a storage disk. In another technique, referred to as bit-patterned media (BPM), high density tracks of magnetic islands are preformed on the surface of the storage disk, and bits of data are written to respective ones of these islands. Nonetheless, ITI remains an important performance issue with these and other HDD recording techniques.
The ITI performance issue may be addressed in some cases by performing ITI reduction post-processing on data read from the storage disk. However, such post-processing requires that interfering data be read from the storage and stored in memory, which can increase HDD cost and complexity while also adversely impacting other performance measures such as access time.
In these and other conventional HDD implementations, a preamplifier driving the read/write head generally provides a write signal having substantially fixed characteristics. The characteristics of the write signal waveform are usually set to optimize overall bit error rate (BER) of the HDD, which can lead to deleterious effects such as varying track widths.